3GPP (3rd Generation Partnership Project) is a project in which the specifications of a mobile communication system based on a network obtained by developing W-CDMA (Wideband-Code Division Multiple Access) and GSM (Global System for Mobile Communications) are examined and produced. In the 3GPP, the W-CDMA method is standardized as a third-generation cellular mobile communication method, and its serves are started one after another. Moreover, HSDPA (High-speed Downlink Packet Access) in which its communication speed is further increased is standardized, and its serves are started. In the 3GPP, the evolution of a third-generation radio access technology (hereinafter also referred to as “LTE (Long Term Evolution” or “EUTRA (Evolved Universal Terrestrial Radio Access”) and a mobile communication system (hereinafter also referred to as “LTE-A (Long Term Evolution-Advanced” or “Advanced-EUTRA”) in which a wider frequency band is utilized to realize higher speed exchange of data are being examined.
As the communication scheme of the LTE, an OFDMA (Orthogonal Frequency Division Multiple Access) method in which subcarriers orthogonal to each other are used to perform user multiplexing and an SC-FDMA (Single Carrier-Frequency Division Multiple Access) method are being examined. In other words, in the downlink, the OFDMA method, which is a multicarrier communication method, is proposed, and in the uplink, the SC-FDMA method, which is a single carrier communication method, is proposed.
On the other hand, as the communication method of the LTE-A, in the downlink, the introduction of the OFDMA method is being examined, and in the uplink, in addition to the SC-FDMA method, the introduction of a Clustered-SC-FDMA (Clustered-Single Carrier-Frequency Division Multiple Access; which is also referred to as a DFT-s-OFDM with Spectrum Division Control or a DFT-precoded OFDM) method is being examined. In the LTE and the LTE-A, the SC-FDMA method and the Clustered-SC-FDMA method proposed as the uplink communication method can reduce, in the characteristic of the single carrier communication method (due to the single carrier characteristic), a PAPR (Peak to Average Power Ratio: transmission power) when data (information) is transmitted.
While a frequency band used in a general mobile communication system is contiguous, in the LTE-A, it is proposed that a plurality of frequency bands which are contiguous and/or non-contiguous (hereinafter also referred to as a “CC: Component Carrier” or a “CC: Carrier Component”) are compositely used and are utilized as one wider frequency band (also referred to as frequency band aggregation: Carrier Aggregation). Moreover, in order for the base station apparatus and the mobile station apparatus to more flexibly use a wider frequency band to perform communication, it is proposed that a frequency band used for downlink communication and a frequency band used for uplink communication are made different in frequency bandwidth (asymmetric frequency band aggregation: Asymmetric carrier aggregation) (non-patent document 1).
FIG. 8 is a diagram illustrating a mobile communication system subjected to frequency band aggregation in a conventional technology. That a frequency band used for downlink (DL: Down Link) communication as shown in FIG. 8 and a frequency band used for uplink (UL: Up Link) communication are made equal in frequency bandwidth is also referred to as symmetric frequency band aggregation (Symmetric carrier aggregation). As shown in FIG. 8, the base station apparatus and the mobile station apparatus compositely use a plurality of component carriers that are contiguous and/or non-contiguous frequency bands, and thereby can perform communication in a wider frequency band which is composed of a plurality of component carriers.
FIG. 8 shows, as an example, that a frequency band (which may be a DL system band (width)) having a bandwidth of 100 MHz and used in the downlink communication, which is composed of five downlink component carriers (DCC1: Downlink Component Carrier1, DCC2, DCC3, DCC4, DCC5) having a bandwidth of 20 MHz. FIG. 8 also shows, as an example, that a frequency band (which may be a UL system band (width)) having a bandwidth of 100 MHz and used in the uplink communication, which is composed of five uplink component carriers (UCC1: Uplink Component Carrier1, UCC2, UCC3, UCC4, UCC5) having a bandwidth of 20 MHz.
In FIG. 8, on each downlink component carrier, downlink channels such as a physical downlink control channel (hereinafter, PDCCH: Physical Downlink Control Channel) and a physical downlink shared channel (hereinafter, PDSCH: Physical Downlink Shared Channel) are mapped.
The base station apparatus uses the PDCCH to allocate (schedule) downlink control information (DCI: Downlink Control Information) for transmitting a downlink transport block transmitted using the PDSCH to the mobile station apparatus, and uses the PDSCH to transmit the downlink transport block to the mobile station apparatus. Here, in FIG. 8, the base station apparatus can transmit, at the maximum, up to five downlink transport blocks (which may be the PDSCH) in the same subframe to the mobile station apparatus.
On each uplink component carrier, uplink channels such as a physical uplink control channel (hereinafter, PUCCH: Physical Uplink Control Channel) and a physical uplink shared channel (hereinafter, PUSCH: Physical Uplink Shared Channel) are mapped.
The mobile station apparatus uses the PDCCH and/or the PUSCH to transmit, to the base station apparatus, uplink control information (UCI: Uplink Control Information) such as channel state information (CSI: Channel Statement Information) indicating the channel state of the downlink, information indicating an ACK/NACK (Positive Acknowledgement/Negative Acknowledgement) of a HARQ (Hybrid Automatic Repeat Request) for the downlink transport block, and scheduling request (SR: scheduling request). Here, in FIG. 8, the mobile station apparatus can transmit, at the maximum, up to five uplink transport blocks (which may be the PUSCH) in the same subframe to the base station apparatus.
Likewise, FIG. 9 is a diagram illustrating a mobile communication system subjected to asymmetric frequency band aggregation in the conventional technology. As shown in FIG. 9, the base station apparatus and the mobile station apparatus make a frequency band used for downlink communication and a frequency band used for uplink communication different in frequency bandwidth, compositely use component carriers that form these frequency bands and that are contiguous and/or non-contiguous frequency bands, and thereby can perform communication in a broad frequency band.
FIG. 9 shows, as an example, that a frequency band having a bandwidth of 100 MHz and used in the downlink communication, which is composed of five downlink component carriers (DCC1, DCC2, DCC3, DCC4, DCC5) having a bandwidth of 20 MHz. FIG. 9 also shows, as an example, that a frequency band having a bandwidth of 40 MHz and used in the uplink communication, which is composed of two uplink component carriers (UCC1 and UCC2) having a bandwidth of 20 MHz.
In FIG. 9, the downlink/uplink channels are mapped on each of the downlink/uplink component carriers, and the base station apparatus uses the PDSCH to allocate (schedule) the PDSCH to the mobile station apparatus, and uses the PDSCH to transmit the downlink transport block to the mobile station apparatus. Here, in FIG. 9, the base station apparatus can transmit, at the maximum, up to five downlink transport blocks (which may be the PDSCH) in the same subframe to the mobile station apparatus.
The mobile station apparatus uses the PUCCH and/or the PUSCH to transmit, to the base station apparatus, the uplink control information such as the channel state information, the information indicating an ACK/NACK of the HARQ for the downlink transport block, and the scheduling request. Here, in FIG. 9, the mobile station apparatus can transmit, at the maximum, up to two uplink transport blocks (which may be the PUSCH) in the same subframe to the base station apparatus.
Furthermore, in the LTE-A, in order for the base station apparatus to measure the uplink channel, an examination is performed in which the mobile station apparatus transmits a reference signal (hereinafter also referred to as a sounding reference signal, SRS: Sounding Reference Signal) to the base station apparatus using the uplink. The base station apparatus schedules, based on the SRS transmitted from the mobile station apparatus, the mobile station apparatus, and performs, for example, the allocation of PUSCH resources, the determination of a modulation scheme to be carried out on the PUSCH and a coding rate and the like.
With respect to the transmission of the SRS by the mobile station apparatus, an examination is performed in which, the base station apparatus provides, for the mobile station apparatus, an instruction (request, trigger) of the transmission of an aperiodic SRS (hereinafter also referred to as an A-SRS: Aperiodic SRS, Dynamic SRS or Scheduled SRS), in addition to the transmission of a periodic SRS (hereinafter also referred to as a P-SRS: Periodic SRS). For example, it is proposed that the base station apparatus uses, for mobile station apparatus, a downlink control information format (hereinafter also referred to as a DCI format, a Downlink grant or a Downlink assignment) for the downlink to provide an instruction of the transmission of the A-SRS (non-patent document 2). For example, it is proposed that the base station apparatus uses, for mobile station apparatus, a downlink control information format (hereinafter also referred to as a DCI format, an Uplink grant or an Uplink assignment) for the uplink to provide an instruction of the transmission of the A-SRS (non-patent document 3).